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authorH. Peter Anvin <hpa@linux.intel.com>2014-02-13 15:46:04 (GMT)
committerH. Peter Anvin <hpa@linux.intel.com>2014-02-13 16:40:52 (GMT)
commit4640c7ee9b8953237d05a61ea3ea93981d1bc961 (patch)
tree580aa78183348a9cfcea51a50b1cc4e8ef5a309f /arch/x86/mm
parent03bbd596ac04fef47ce93a730b8f086d797c3021 (diff)
x86, smap: smap_violation() is bogus if CONFIG_X86_SMAP is off
If CONFIG_X86_SMAP is disabled, smap_violation() tests for conditions which are incorrect (as the AC flag doesn't matter), causing spurious faults. The dynamic disabling of SMAP (nosmap on the command line) is fine because it disables X86_FEATURE_SMAP, therefore causing the static_cpu_has() to return false. Found by Fengguang Wu's test system. [ v3: move all predicates into smap_violation() ] [ v2: use IS_ENABLED() instead of #ifdef ] Reported-by: Fengguang Wu <fengguang.wu@intel.com> Link: http://lkml.kernel.org/r/20140213124550.GA30497@localhost Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: <stable@vger.kernel.org> # v3.7+
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/fault.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 9d591c8..6dea040 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1001,6 +1001,12 @@ static int fault_in_kernel_space(unsigned long address)
static inline bool smap_violation(int error_code, struct pt_regs *regs)
{
+ if (!IS_ENABLED(CONFIG_X86_SMAP))
+ return false;
+
+ if (!static_cpu_has(X86_FEATURE_SMAP))
+ return false;
+
if (error_code & PF_USER)
return false;
@@ -1087,11 +1093,9 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code)
if (unlikely(error_code & PF_RSVD))
pgtable_bad(regs, error_code, address);
- if (static_cpu_has(X86_FEATURE_SMAP)) {
- if (unlikely(smap_violation(error_code, regs))) {
- bad_area_nosemaphore(regs, error_code, address);
- return;
- }
+ if (unlikely(smap_violation(error_code, regs))) {
+ bad_area_nosemaphore(regs, error_code, address);
+ return;
}
/*

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